the keyboard I found with the XT has no model number or markings (no evidence that there was ever any). The badge on top just say IBM Personal Computer.
weighs a ton.. as I think it is all metal construction.. and function keys are all on the left side
anyway of telling what model it is?
Well, for starters, 'model' isn't quite right - frustrating that IBM used the terms 'Model M' and 'Model F', since those describe the keyswitch mechanisms, not the keyboards. It's quite misleading to people who don't know "way too much" about keyboards. Nothing wrong with referring to them that way, just need to add further descriptive terms for clarity.
But what you have is the original keyboard for the PC and XT, aka "XT Model F". It is significantly less valuable on the open market than the AT board because it is not 'plug and play' on modern systems or off-the-shelf USB converters.
Would seem to be damned easy to get converters set up though, particularly with the availability of user-friendly access to AVR microcontrollers like the Teensy (even if overpowered for the job, it's ridiculously easy to work with, so the additional cost is worth it as a headache-saver). There are a couple such initiatives (XT keyboard to AT, instead of the inverse which you find here) at that site whose name I mentioned a couple posts up.
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As for my own 'Must Haves':
I'm into 'this stuff' for fun, so I have something to tinker with. I'm less interested, I suppose, in what I could use the system for, or nostalgia, or whatever (I'm 21, it's not really possible for it to be nostalgia)...which is why, after I got my 286 back on its feet, played a couple games, I more or less abandoned it for the XT rebuild project (which required actually building the thing).
My current project is attempting to max out the specs of that Dolch luggable system I linked to some time ago now. After it's all good to go I'll probably move on to something new.